Microsoft rolled out the August 2025 cumulative update for Windows 11 version 24H2, also known as KB5063878.The update was supposed to fix problems with game performance and some app slowdowns, which had been frustrating gamers for months.
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Microsoft rolled out the August 2025 cumulative update for Windows 11 version 24H2, also known as KB5063878. The update was supposed to fix problems with game performance and some app slowdowns, which had been frustrating gamers for months. But instead of smoothing things out, this patch has opened up a new problem: it's causing certain SSDs to fail when writing large numbers of files.The issue isn't universal, but it seems to heavily affect solid-state drives that use Phison controllers. Users began reporting that their systems became unstable when copying or writing large amounts of data, usually in the range of 50 GB or more. In these cases, the drive can suddenly stop functioning properly. After a reboot, Windows may no longer recognize the SSD at all, leaving the partition inaccessible. For anyone storing important files on one of these drives, the risk is significant.
The problem goes beyond consumer systems too. IT administrators using corporate deployment tools such as WSUS and SCCM have noticed another bug tied to this update: error code 0x80240069, which blocks the update from being installed across managed devices. While that's frustrating in an enterprise environment, the SSD failures are more concerning for everyday users, especially because the issue involves potential data loss.
Several SSD models have been singled out as being most vulnerable. These include the Corsair Force MP600, SSDs built around the Phison PS5012-E12 controller, Kioxia Exceria Plus G4, Fikwot FN955, and SanDisk Extreme Pro M.2 NVMe 3D. Reports suggest that once the failure occurs, the operating system can no longer access the partition, forcing a full reformat or even hardware replacement in some cases.
At the moment, the safest course of action is to avoid running extended write operations if you have installed the KB5063878 update and use one of these drives. Tasks such as large backups, moving huge folders, or continuous write-heavy workloads should be postponed until Microsoft releases a fix. If avoiding these tasks isn't an option, making regular backups to an unaffected drive or cloud storage is strongly advised.
For now, Windows 11 users should approach KB5063878 with caution. If your system relies on a Phison-based SSD, particularly one of the listed models, you may want to hold off on applying the update or be prepared to limit heavy file transfers until further information is available.